Computational Estimation And RANS Simulation of Free Surface Flow Around A Ship Hull

Ship hydrodynamics present many unique challenges due to complex geometry, environment, and operating conditions, which results in many complex physics and modelling issues. This is commonly studied through experiments in a towing tank and experiments in a sea keeping and manoeuvring basin. Recently hydrodynamicists have begun to venture into computational prediction of hydrodynamic behaviour of surface ships. Free surface phenomenon around a ship hull plays an important role in its resistance. Wave making resistance comes from the very presence of free surface. Therefore its accurate prediction is very essential for ship design. The flow problem to be simulated is rich in complexity and poses many modelling challenges because of the existence of breaking waves around the ship hull involving two-phase flow, and because of the resolution of thin turbulent boundary layer. The paper aims to computationally estimate the effect of free surface for a moving ship. Commercial software is used for grid generation and flow solution. 1. Solution of a Rudder of a ship in submerged condition. Few different shapes of the rudders are examined. 2. Solution of flow- around a complete ship with free surface. In the present work, flow through the ship hull is computed using a finite volume commercial code, ANSYS 12.1. The ship geometry is modelled using solid modelling software, CATIA V5R9. A three-dimensional structured hexahedral grid is generated using grid generating code, ICEM-CFD V10.0 .Turbulence is modelled with Reynolds Stress model. The resistance of the ship is predicted, and compared against the experimental values. The rudder of the ship is also analyzed. Two different shapes, one wedge shaped and a standard NACA0012 foil, for which experimental results are available in literature, are analyzed. The lift coefficients and flow separation are predicted for different angles of attack using various turbulence models.Computational results are in good agreement with the experimental ones

Artificial Micro-Swimmers in Simulated Natural Environments

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Efficient simulation of communication systems on a desktop grid

Simulation is an important part of the design cycle of modern communication systems. As communication systems grow more sophisticated, the computational burden of these simulations can become excessive. The need to rapidly bring systems to market generally precludes the use of a single computer, and drives a demand for parallel computation. While this demand could be satisfied by the development of dedicated infrastructure, a more efficient option is to harness the unused computational cycles of underutilized desktop computers located throughout the organization.;In this thesis, a new paradigm for parallelizing communication simulations is proposed and developed. A desktop grid is created by running a compute engine as a background job on existing computers located throughout the University. The compute engine takes advantage of unused cycles to run simulations, and reports its results back to a server. The simulation itself is developed and launched from a client machine using Matlab, an application that has widespread acceptance within the communications industry. To obviate the need for a Matlab license on every machine running the compute engine, the simulation is first compiled to stand-alone executable code, and the executable and input data files are distributed to the grid machines over the Internet. To illustrate the performance improvement, a campaign of 16 distinct simulations corresponding to the IEEE 802.11a standard is run over the grid. Each compute engine executes a single simulation corresponding to one of eight modulation and coding schemes and one of two channel models. The improvement in execution time is quantified by a tool that was developed to monitor the activity of the grid

Biodegradation of the Azo Dye Airedale Yellow CHD: Understanding using residuals

Textile industries are heavy users of water and also produce lots of contaminated effluents. The main contaminants are azo dyes. Hence, the effluents are to be treated before leaving in the environment. In this study, the azo dye Airedale Yellow CHD was biodegraded using two bacteria Thalassospira frigidphilosprofundus (NCIM no 5438) and Erwinia chrysanthemi Burkholder (NCIM no 5213) in shaking conical flasks. Effect of Various parameters like pH, temperature, agitation, and concentration of dye solution on its decolorization was investigated. The biodegradation was statistically worked out using MINITAB software for the ANOVA. The residual plots along with the scatter plots for the decolorization of Airedale Yellow CHD using T. frigidphilosprofundus and E. chrysanthemi Burkholder are also obtained and included in this work. The maximum percent removal of the azo dye was obtained by using T. frigidphilosprofundus (77.41%) whereas it was reported at 74.64% by using E. chrysanthemi Burkholder. The obtained results formed a good fit according to the obtained normal residual plot which can conclude that the findings of the study are accurate and satisfactory

Draft genome sequence of Desulfuromonas acetexigens strain 2873, a novel anode-respiring bacterium

Here, we report the draft genome sequence of Desulfuromonas acetexigens strain 2873, which was originally isolated from digester sludge from a sewage treatment plant in Germany. This bacterium is capable of anode respiration with high electrochemical activity in microbial electrochemical systems. The draft genome contains 3,376 predicted protein-coding genes and putative multiheme c-type cytochromes

Synthesis of an amorphous Geobacter-manganese oxide biohybrid as an efficient water oxidation catalyst

The development of a low cost and efficient oxygen evolution reaction (OER) catalyst has paramount importance to meet the future sustainable energy demand. Nature's photosynthetic machinery deploy manganese-based complex in the photosystem II to oxidize water. Inspired by nature, herein, we synthesized a high performing manganese-based OER catalyst using an electrochemically active and iron-rich bacterium, Geobacter sulfurreducens. The as-synthesized biohybrid catalyst (amorphous Geobacter-Mn2O3) produced a current density of 10 mA cm−2 at an overpotential of 290 ± 9 mV versus a reversible hydrogen electrode with a low Tafel slope of 59 mV dec−1. The catalyst exhibited remarkable stability, evidenced through a long-term chronopotentiometry experiment. Multiple evidence showed that G. sulfurreducens contributed OER active elements (iron and phosphorus) to the biohybrid catalyst, and the as-synthesized Geobacter-Mn2O3 is amorphous. The amorphous structure of the biohybrid catalyst provided a large electrochemically active surface area and excess catalytic sites for the OER catalysis. In addition, Mn3+ present in the biohybrid catalyst is believed to be the precursor for oxygen evolution. The OER activity of the biohybrid catalyst outperformed commercial-Mn2O3, commercial-IrO2 and most of the benchmark precious OER catalysts, thus supporting its suitability for large-scale applications. The proposed green approach to synthesize a biohybrid catalyst paves a new avenue to develop robust and cost-effective electrocatalysts for energy-related applications

Artificial micro-swimmers in simulated natural environments

Microswimmers, such as bacteria, are known to show different behaviours depending on their local environment. They identify spatial chemical gradients to find nutrient rich areas (chemotaxis) and interact with shear flows to accumulate in high shear regions. Recently, artificial microswimmers have been developed which mimic their natural counterparts in many ways. One of the exciting topics in this field is to study these artificial motors in several natural settings like the ones bacteria interact with. In this Focus article, we summarize recent observations of artificial swimmers in chemical gradients, shear flows and other interesting natural environments simulated in the lab using microfluidics and nanotechnology

Motion in microfluidic ratchets

The ubiquitous random motion of mesoscopic active particles, such as cells, can be "rectified" or directed by embedding the particles in systems containing local and periodic asymmetric cues. Incorporated on lab-on-a-chip devices, these microratchet-like structures can be used to self-propel fluids, transport particles, and direct cell motion in the absence of external power sources. In this Focus article we discuss recent advances in the use of ratchet-like geometries in microfluidics which could open new avenues in biomedicine for applications in diagnosis, cancer biology, and bioengineering

Bioinspired Synthesis of Reduced Graphene Oxide-Wrapped Geobacter sulfurreducens as a Hybrid Electrocatalyst for Efficient Oxygen Evolution Reaction

Doping/decorating of graphene or reduced graphene oxide (rGO) with heteroatoms provides a promising route for the development of electrocatalysts which will be useful in many technologies, including water splitting. However, current doping approaches are complicated, not eco-friendly, and not cost-effective. Herein, we report the synthesis of doped/decorated rGO for oxygen evolution reaction (OER) using a simple approach that is cost-effective, sustainable, and easy to scale up. The OER catalyst was derived from the reduction of GO by an exo-electron-transferring bacterium, Geobacter sulfurreducens. Various analytical tools indicate that OER active elements such as Fe, Cu, N, P, and S decorate the rGO flakes. The hybrid catalyst (i.e., Geobacter/rGO) produces a geometric current density of 10 mA cm–2 at an overpotential of 270 mV versus the reversible hydrogen electrode with a Tafel slope of 43 mV dec–1 and possesses high durability, as evidenced through 10 h of stability testing. Electrochemical analyses suggest the importance of Fe and its possible role as an active site for OER. Overall, this work represents a simple approach toward the development of an earth-abundant, eco-friendly, and highly active OER electrocatalyst for various applications such as solar fuel production, rechargeable metal–air batteries, and microbial electrosynthesis

The open circuit potential of Geobacter sulfurreducens bioanodes depends on the electrochemical adaptation of the strain

Bioanodes for acetate oxidation were formed with pure cultures of Geobacter sulfurreducens under constant polarization potential. With the original commercial strain, the bioanodes formed at + 0.2 V/SCE exhibited open circuit potential (OCP) of 0.0 V/SCE, while the bioanodes formed at − 0.2 V/SCE had OCP around − 0.52 V/SCE. In contrast, the bioanodes formed with bacterial cells collected from a previous current-producing bioanode exhibited OCP of − 0.52 V/SCE whatever the polarization potential used to form them (+ 0.2 V/SCE or − 0.2 V/SCE). The "electrochemically-adapted strain" kept its electrochemical characteristics after successive cultures in solution. High steady-state currents were reached (16-19 A m- 2) in all cases without any dependence on strain adaptation or applied potential